Wireless Access Point Cell ID Insertion in Frame Header

ABSTRACT

A wireless access point includes a wireless interface to send or receive frames in a cell in a wireless network. A storage device stores a cell ID that uniquely identifies the wireless access point. Processing circuitry inserts the cell ID in a physical layer header of a frame, and sends the frame to a client device in the cell via the wireless interface.

BACKGROUND

A client in a wireless network associates with a wireless access point(WAP) to get connectivity, for example, to and from the Internet, and tofurther communicate with other clients via the wireless network. Aclient typically relies on one WAP at any given time for allcommunications in the wireless network. Commonly, the wireless networkincludes multiple WAPs, each servicing its own set of clients. In thesesituations, communications from neighboring WAPs may interfere withcommunications between a WAP and its client.

BRIEF DESCRIPTION OF DRAWINGS

The embodiments are described in detail with reference to the examplesshown in the following figures:

FIG. 1 illustrates wireless access points (WAP and clients in a wirelessnetwork;

FIG. 2 illustrates a hardware platform;

FIG. 3 illustrates a method for receiving a frame in a wireless network;and

FIG. 4 illustrates a method for determining a cell ID for a WAP.

DETAILED DESCRIPTION OF EMBODIMENTS

For simplicity and illustrative purposes, the principles of theembodiments are described by referring mainly to examples thereof. Inthe following description details are set forth in order to provide athorough understanding of the embodiments. It is apparent that theembodiments may be practiced without limitation to all the specificdetails. Also, the embodiments may be used together in variouscombinations.

According to an embodiment, a cell ID is included in a frame header todetermine whether a frame is for a network device in a cell in awireless network. For example, a client in a cell may communicate with awireless access point (WAP) in the cell on a channel. Interference mayoccur from communications in a neighboring cell using the same channel.For example, if a radio of a network device (e.g., WAP or client device)detects a valid frame preamble and decodes its physical layer header,the radio locks on to the frame until the entire frame is receivedregardless of whether the frame is destined to it or not. The mediaaccess control (MAC) destination address is a part of physical layerdata payload of the frame. Thus, the MAC destination address cannot beused to decide whether or not to keep receiving the current frame untilthe payload is received and decoded. Locking on unnecessary framesaffects performance because if a desired frame arrives when the receiverhas already locked on a previously arrived interfering frame, thereceiving device in most cases cannot receive the desired frame. Also,the locking on the interfering frame also causes a physical layer (PHY)carrier sense indicator to be in a BUSY state, thus blocking the radiofrom transmitting its own frame. Hence, the locking problem hurtstransmission and reception throughput performance.

According to an embodiment, a unique cell ID is determined for the cellthat is different than a cell ID used by other WAPs in neighboring cellsthat may be using the same channel. The cell ID is included in a headerof the frame, so the entire frame does not need to be received anddecoded by the destination device (e.g., client device or WAP) todetermine whether the frame is destined for it. The cell ID may be in aphysical layer header of the frame. For example, the cell ID may be in a802.11 PHY level header (e.g., PLCP). Before receiving and decoding thepayload and the entire frame, the client device decodes the physicallayer header, which comes ahead of the payload, to determine the cell IDin the header, which may then be used to determine whether the frame isfor the receiving device. If the frame is not for the receiving device,the destination device is then released to send or receive other frames,thus improving throughput for the destination device.

FIG. 1 illustrates a block diagram of a system 100. The system 100includes a wireless network 103. The wireless network 103 may beconnected to the Internet 101, or an access network or any wide areanetwork (WAN) or other network, and not just the Internet 101.

The wireless network 103 includes a router 102, multiple WAPs, shown asWAPs A-B, and multiple clients 1-3. Cells 120 a-b, including a WAP andits associated client(s). More or less than two WAPs and two cells, morerouters and more or less clients may exist in each cell in the wirelessnetwork 103. The number of network devices shown is for illustrationpurposes.

An WAP is a device that allows wireless communication devices, such asclients, to connect to a wireless network using a standard, such as an802.11 standard or other type of standard. The WAPs A-B include networkinterfaces equipped for interfacing with the router 102, another networkoutside the wireless network 103 (e.g., the Internet or an accessnetwork) via the router 102, and the client devices 1-3. The WAPs A-Bmay connect to the router 102 through a wireless or wired connection. Aclient device (also referred to as a client) is a device with a wirelessnetwork interface for connecting to a wireless network, and may includean end user device, such as a laptop, desktop computer, cell phone, etc.The wireless network interface is commonly referred to as a radio.Network devices are any devices that communicate via a wireless network,such as clients and WAPs. A cell comprises a WAP and may include atleast one client that is served by the WAP to communicate via thewireless network. A cell may exist without any clients especially sinceclients may be mobile and move from one cell to another. A WAP withoutclients may still send periodic beacons which are described in furtherdetail below. Cell size may be based on the number of clients the WAPcan support and the communication range of the WAP.

In FIG. 1, each of the clients 1-3 is wirelessly connected to one of theWAPs A-B. The clients 1-3 may be connected to the Internet 101 via oneof the WAPs A-B and the router 102. For example, the clients 1-3 mayreceive different types of data flows, such as VoIP, multiplayer gamedata, streaming video or audio, or bulk transfer of data.

The WAPs A-B include cell ID determination modules 110 a-b cell IDinserter modules 111 a-b and cell ID detector modules 112 a-b. A modulemay be hardware or machine readable instructions executed by hardware,such as a processor or processing circuitry. The cell ID determinationmodules 110 a-b determine unique cell IDs for each cell. For example,the cell ID determination modules 110 a randomly selects a non-zero cellID that is not used by other WAPs operating in the same channel in agiven area associated with the range of the WAP A. A channel may be afrequency or range of frequencies for communicating within the wirelessnetwork. Each WAP may broadcast its cell ID in a beacon in the channelso other WAPs operating in the same channel and within range know thecell IDs of each other and can select a cell ID not used by another WAP.The beacon is broadcasted, so clients on the broadcast channel alsoreceive the beacon. The beacon also includes the MAC address of the WAP,which may be provided as the basic service set identification (BSSID) inan 802.11 beacon. For example, WAP A sends a beacon on the channel usedby client 1, and the beacon includes the cell ID and the MAC address ofWAP A. Client 1 receives the beacon and can determine from the MACaddress that the beacon is from WAP A and stores the cell ID.

The cell ID inserter modules 111 a-b insert their cell IDs in theheaders of frames sent from WAPs A-B to their clients. For example, thecell ID inserter module 111 a inserts the cell ID of WAP A in the header(e.g., physical layer header) of frames sent by WAP A. The cell ID maybe inserted in a cell ID field of a physical layer header. For 802.11,existing fields or portions of existing fields in the PHY header may beused as the cell ID field. The number of bits in the cell ID field maybe based on the number of cells that need unique IDs.

The cell ID detector modules 112 a-b determine the cell ID from receivedframes. For example, the cell ID detector module 112 a checks the PHYheader of a received frame sent by client 1 to determine whether itincludes a non-zero cell ID. If it includes a non-zero cell ID, itcompares the cell ID to the cell ID of WAP A, which may be stored in theradio of WAP A. If the cell ID matches the cell ID of WAP A then itcontinues to receive the frame, or else, it stops receiving the frameand then may send or receive another frame.

The clients 1-3 may include cell ID inserter modules 121 a-c and cell IDdetector modules 122 a-c that perform the same functions as the cell IDinserter modules and detector modules of the WAPs. For example, the cellID inserter module 121 a inserts the cell ID of WAP A in the physicallayer header of outgoing frames destined for the WAP A. The cell IDdetector module 122 a checks the physical layer header of a receivedframe to determine whether it includes a non-zero cell ID. If itincludes a non-zero cell ID, it compares the cell ID to the cell ID ofWAP A, which may be stored in the radio of client 1. If the cell IDmatches the cell ID of WAP A then it continues to receive the frame, orelse, it stops receiving the frame and then may send or receive anotherframe. For example, if the cell ID matches the cell ID of WAP A, client1 determines the frame is from WAP A and continues to receive the frame.If the cell ID does not match, client 1 determines the frame is aninterfering frame and that it is not the destination for the frame.Client 1 then stops receiving the frame and may send or receive anotherframe.

In 802.11, if the radio is locked on a frame currently being received, anew frame must be at least 10 dB stronger than the locked frame for theradio to stop receiving and decoding the current frame and startreceiving and decoding the new frame. By using the cell ID, the radiomay stop receiving the current frame regardless of the signal strengthof the new frame if the current frame does not have a matching cell IDin the header.

The cell ID detector module 122 a may also determine if a messagereceived from WAP A is a beacon, for example based on information in theheader. If it is a beacon, client 1 determines if the beacon is from WAPA by comparing the MAC address of WAP A with a MAC address in thebeacon. If it is a beacon from WAP A, the cell ID is extracted from thepayload of the beacon and stored in client 1.

FIG. 2 illustrates a hardware platform 200 of a network device. Thehardware platform may be a platform for a WAP or a client shown inFIG. 1. The components shown in the hardware platform 200 may be used indifferent types of network devices but the different types of networkdevices ma include different components as well that are not shown. Thehardware platform 200 includes one or more processors or processingcircuitry (e.g., application-specific integrated circuit) represented byprocessor 202, providing an execution platform for executing machinereadable instructions including software. The processor 202 may processa frame according to executed machine readable instructions, includingpreparing, sending and/or forwarding frames to a destination. Commandsand data from the processor 202 are communicated over a communicationbus 203. The hardware platform 200 also includes non-transitory computerreadable storage mediums including a memory 204, such as a Random AccessMemory (RAM), where software is resident during runtime, and a secondarystorage 208. The secondary storage 208 may include nonvolatile datastorage where a copy of the software and data are stored.

The memory 204 may store modules that are comprised of machine readableinstructions executable by the processor 202 at runtime. Some examplesof modules in the memory 204 are shown. For example, a memory cell IDdetermination module 210 and a cell ID inserter module 211 may be storedin the memory 204. The cell ID determination module 210 may include themodule 110 a or 110 b shown in FIG. 1 if the hardware platform 200 isused in a WAP. The cell ID inserter module 211 may include the modules111 a-c or 121 a-c shown in FIG. 1. Other modules may be stored in thememory 204 at runtime.

The hardware platform 200 includes a wireless interface 221 forcommunicating in a wireless network. The wireless interface 221 may be aradio in a WAP or client. The wireless interface 221 may include memory222 and processing circuitry 223. The memory 222 and processingcircuitry 223 may be provided in a chipset. The memory 222 may store acell ID 215 of a WAP, which is used to determine whether a receivedframe is destined for the receiving device. The cell ID 215 may also bestored in the memory 204. Some modules may be in the wireless interface221 and may be hardware only or machine readable instructions executedby hardware. In one example, cell ID detector module 212 may be in thewireless interface 221. For example, the cell ID detector module 212 maybe the module 112 a-b or 122 a-c as shown in FIG. 1, and determines thecell ID from a physical layer header in a received frame and comparesthe cell ID from the frame with the cell ID 215 to determine whether theframe is destined for the receiving device. Other modules may beembodied in the wireless interface 221, such as the cell ID insertermodule 211.

FIG. 3 shows an example of a method 300 for receiving a frame in awireless network. The methods 300 and 400, described below, aredescribed with respect to the system 100 shown in FIG. 1 by way ofexample. For example, the method 300 may be performed by a WAP or aclient device shown in FIG. 1 and the method 400 may be performed by aWAP shown in FIG. 1. The methods may be performed by other systems.

At 301, a frame is received at a network device. The network device mayinclude a WAP or a client device shown in FIG. 1 or any device thatcommunicates with a WAP to send or receive data in the wireless network.

At 302, a cell ID is determined from a header of the frame, for example,by a cell ID determination module shown in FIG. 1. The cell ID may be ina physical layer header of the frame. For example, the cell ID is in a802.11 PHY level header (e.g., PLCP header)rather than in a payload of aframe. Before receiving and decoding the payload and the entire frame,the receiving device decodes the physical layer header, which comesahead of the payload, to determine the cell ID in the physical layerheader, which may then be used to determine whether the frame is for thereceiving device. As described below, if the frame is not for thereceiving device, the receiving device is then released to send orreceive other frames without having to decode the payload, thusimproving throughput for the receiving device.

At 303, a determination is made as to whether the cell ID in the headermatches a stored cell ID for a WAP, for example, by a cell IDdetermination module shown in FIG. 1. If the cell ID from the headermatches the stored cell ID, at 304, the network device continuesreceiving the frame at the network device. For example, the frameheaders and payload are received and decoded. If the cell ID from theheader does not match the stored cell ID, at 305, the network device isreleased to send or receive another frame. For example, the networkdevice stops receiving the frame and may send or receive another frame.If sending another frame, the network device may determine whether asignal strength is below a carrier sense threshold before sending toavoid interference.

FIG. 4 illustrates a method for determining a cell ID. A WAP maydetermine the cell ID. At 401, the WAP selects a cell ID. For example,the WAP may randomly select a cell ID that is not used by another WAP.The WAP may store cell IDs used by its neighbor WAPs and selects a cellID that is not being used.

At 402, the WAP broadcasts the selected cell ID. The broadcast may bereceived by any client device or WAP in the wireless network that iswithin range. For example, the WAP sends a beacon with the selected cellID. The beacon may be transmitted on the channel used by the WAP tocommunicate with its clients in its cell. The beacon message includesthe cell ID in its payload, for example, in an 802.11 beacon informationelement. Clients that are in the WAP's cell store the cell ID of the WAPso the clients can use the cell ID to determine whether a received frameis from the WAP or another network device. Also, neighbor WAPs that arewithin range of the WAP may store the cell ID of the WAP. For example,neighbor WAPs on the same channel may interfere with communications inthe WAP's cell. The neighbor WAPs may store the cell ID of the WAP sothey do not use the same cell ID. Neighbor WAPs may be WAPs within rangeof each other.

In certain instances the WAP may not know the cell IDs of all itsneighbors that may interfere. For example, if the WAP is new or justswitched to the channel, it may not have the cell Ds of all itsneighbors using the channel. At 403, the WAP determines whether itreceives any messages from neighbor WAPs indicating that its cell ID isbeing used by another WAP. If so, the WAP selects and broadcasts anothercell ID. In one example, beacons may be sent periodically (e.g., every100 milliseconds), so it is less likely that a WAP would not know itsneighbor cell IDs and it is less likely the WAP selects a cell IDcurrently being used by a neighbor on the same channel. However, if theWAP receives a message indicating the cell ID is being used by anotherWAP, then the WAP selects and broadcasts a new unique cell ID. If nomessages are received within a predetermined time, the WAP uses the cellID at 404. For example, the WAP inserts the cell ID in the physicallayer header of the frames sent to clients in its cell. In someinstances, beacons or other broadcasted frames meant to be heard bydevices outside the same cell, may have the cell ID field set to zero orempty, instead of filling it with the non-zero cell ID value. In theseinstances, the receiving devices receive and decode the beacons and thebroadcast frames till the end of the frames so the receiving devices canget the information from the payload.

While the embodiments have been described with reference to examples,various modifications to the described embodiments may be made withoutdeparting from the scope of the claimed embodiments.

What is claimed is:
 1. A method of receiving a frame in a wirelessnetwork, the method comprising: receiving the frame at a network device:determining a cell ID in a physical layer header of the frame; if thecell ID from the physical layer header matches a stored cell ID,continue receiving the frame, wherein the stored cell ID uniquelyidentifies a wireless access point; and if the cell ID from the physicallayer header does not match the stored cell ID, releasing the networkdevice to send or receive another frame.
 2. The method of claim 1,wherein if the cell ID from the physical layer header does not match thestored cell ID, stopping the receiving of the frame, and receivinganother frame regardless of a signal strength of the another frame. 3.The method of claim 1, wherein if the cell ID from the physical layerheader does not match the stored cell ID, stopping the receiving of theframe, and sending another frame from the network device.
 4. The methodof claim 3, wherein the sending of the another frame comprises:determining if a signal strength is below a carrier sense threshold;sending the another frame if the signal strength is below the carriersense threshold; and waiting for the signal strength to fall below thecarrier sense threshold to end the another frame if the signal strengthis above the threshold.
 5. The method of claim 1, wherein the networkdevice comprises a client device connected to the wireless access pointin a cell and the method comprises: receiving a broadcast at the clientdevice from the wireless access point; determining the cell ID thatuniquely identifies the wireless access point from the broadcast; andstoring the cell ID in the client device.
 6. The method of claim 5,wherein the determining of the cell ID comprises determining the cell IDin a software layer in the client device and the storing comprisesstoring the cell ID in a memory of a radio in the client device, whereinthe radio determines the cell ID from the physical layer header of theframe.
 7. The method of claim 5, wherein the cell ID is not used bywireless access points in neighboring cells using the same frequency. 8.The method of claim 1, wherein the releasing of the network device tosend or receive another frame comprises sending or receiving the anotherframe prior to decoding a payload of the frame.
 9. A network device in acell in a wireless network, the network device comprising: a wirelessinterface to receive a frame; a storage device to store a cell IDuniquely identifying a wireless access point in the cell; and processingcircuitry to determine a cell ID in a physical layer header of theframe, and if the cell ID from the physical layer header matches thestored cell ID, to continue to receive the frame, and if the cell IDfrom the physical layer header does not match the stored cell ID, torelease the network device to send or receive another frame.
 10. Thenetwork device of claim 9, wherein if the cell ID from the physicallayer header does not match the stored cell ID, the network device stopsreceiving the frame, and receives another frame regardless of a signalstrength of the another frame.
 11. The network device of claim 9,wherein if the cell ID from the physical layer header does not match thestored cell ID, the network device stops receiving the frame and sendsanother frame.
 12. The network device of claim 9, wherein if the cell IDfrom the physical layer header does not match the stored cell ID, theprocessing circuitry is to determine if a signal strength is below acarrier sense threshold, send another frame if the signal strength isbelow the carrier sense threshold, and wait for the signal strength tofall below the carrier sense threshold to send the another frame if thesignal strength is above the threshold.
 13. The network device of claim9, wherein the processing circuitry is to receive a broadcast at theclient device from the wireless access point, determine the cell ID fromthe broadcast, and store the cell ID.
 14. A wireless access pointcomprising: a wireless interface to send or receive frames in a cell ina wireless network; a storage device to store a cell ID uniquelyidentifying a wireless access point in the cell; and processingcircuitry to insert the cell ID in a physical layer header of a frame,and send the frame to a client device in the cell via the wirelessinterface.
 15. The wireless access point of claim 14, wherein thewireless interface is to broadcast the cell ID, and the client devicereceives and stores the cell ID and determines if the cell ID from thephysical layer header matches the cell ID received in the broadcast todetermine if the client device is the destination for the frame.